The present invention relates to the production of monochloroacetic acid from hydroxyacetic acid.
Monochloroacetic acid has long been made by chlorinating acetic acid in the presence of a catalyst and removing from the monochlorinated product dichloroacetic acid and other by-products of the reaction. It is well known that these operations are difficult to accomplish economically in a manner yielding a product of satisfactory purity. The chlorination is usually carried out by passing chlorine into a mixture of glacial acetic acid and acetic anhydride and/or acetyl chloride while heating the mixture under reflux at a reaction temperature, usually from 80.degree. to 110.degree. C., and venting the gaseous hydrogen chloride which is formed. After completing the reaction, the monochloroacetic acid product is crystallized and then subjected to recrystallization and/or solvent extraction operations to remove impurities, especially dichloroacetic acid, down to a point at which the monochloroacetic acid is of a purity acceptable on the market. The dichloroacetic acid boils at close to the same temperature as monochloroacetic acid and cannot satisfactorily be removed by distillation.
The present invention provides a process for producing monochloroacetic acid in such a manner that it is relatively easily separated by distillation from the reaction zone effluent.
According to U.S. Pat. No. 2,503,334, conversion of acetic acid to monochloroacetic acid by chlorination can be carried out in the presence of iodine catalyst.
Other processes which have been disclosed for producing monochloroacetic acid include that of U.S. Pat. No. 935,606, wherein dichloroethoxyethylene is hydrolyzed to monochloroacetic acid and ethanol; and also that of U.S. Pat. No. 2,298,138, which states that chloroacetic acid can be produced by the reaction of formaldehyde with carbon monoxide and hydrogen chloride.
The reaction of primary alcohols with hydrogen chloride in the presence of catalyst is disclosed, for example in U.S. Pat. No. 3,484,494 (vapor-phase reaction of alkanol with hydrogen chloride in the presence of alumina-potassium catalyst) and in Morrison and Boyd, Organic Chemistry, Allyn and Bacon, 1970, page 525 (zinc chloride catalyst).